(1) Field of the Invention
The present invention relates to an image forming apparatus such as a copier, printer, facsimile machine or the like and a toner cartridge for use in the same apparatus.
(2) Description of the Prior Art
A typical image forming apparatus based on an electrophotographic process reproduces images by the steps of forming an electrostatic latent image on a photoconductor surface, developing the electrostatic latent image by using a development unit device to create a toner image and transferring the toner image to printing paper.
Generally, the developing unit is mainly comprised of a developer roller for making toner adhere to the photoconductor surface to form toner images and a toner container for supplying the toner to the developer roller. For user""s convenience or improvement in service performance, the toner container is usually made of a cartridge so as to allow users to readily replace the cartridge.
Since this cartridge configuration enables users to do maintenance of the image forming apparatus by themselves without leaving the maintenance in the charge of professional service persons, it is possible to markedly improve the operativity.
In such cartridge type configurations, a toner cartridge is attached first to a developing unit, then the developing unit is positioned by a mechanically operating device(e.g., leverage action) so that its developer roller comes into pressing contact with a photoconductor. When the toner inside the toner cartridge is consumed and runs out from repeated cycles of image reproduction, the used toner cartridge should be removed and replaced with a new toner cartridge by releasing the pressing force of the developer roller acting on the photoconductor by the mechanically operating device.
However, such a conventional image forming apparatus as described above faces the problem of becoming complex in machine configuration because of the necessity of a mechanically operating device for making pressing contact between the photoconductor and developer roller and the problem that the image forming apparatus could be broken by a wrong handling of the mechanically operating device.
Another problem with the mechanically operating device is that it is difficult to establish uniform pressing contact between the photoconductor and developer roller. This problem occurs due to inclusion of springs in the mechanically operating device. That is, in order for the developer roller to come in uniform contact with the photoconductor, it is necessary that a multiple number of springs should present equal strength of repulsive force. However, as a result of use of a mechanically operating device, the dimensional tolerance and assembly accuracy tolerance of the constituent parts and their dimensional changes due to deformation when the mechanically operating device is operated and other errors build up, hence the spring lengths become different one from another, causing imbalance in strength of repulsive force between the springs.
The present invention has been achieved in view of the above circumstances, and it is therefore an object of the present invention to provide an image forming apparatus with a toner cartridge for use therein, having a simple configuration which allows easy replacement of the toner cartridge and enables a developer roller to abut a photoconductor with a uniform distribution of pressure across the length of the developer roller.
In order to achieve the above object, the arrangement of the image forming apparatus with a toner cartridge according to the present invention uses the following configurations.
A first feature of the present invention resides in an image forming apparatus comprising: a photoconductor which is effective to have latent images formed on the surface thereof; a developing unit having a developer roller rotatably supported by a framework thereof for making toner adhere to the photoconductor surface so as to form a toner image; a toner cartridge removably attached to the framework of the developing unit for supplying toner to the developer roller; and a housing for covering the photoconductor and developing unit, wherein elastic members fixed at one end thereof to the housing are provided, and when the toner cartridge is set into the framework of the developing unit, distal ends of the elastic members abut the toner cartridge so that the elastic members are compressed to produce repulsive force, which acts on the developer roller by way of the toner cartridge and framework so that the developer roller comes into pressing contact with the photoconductor.
A second feature of the present invention resides in the image forming apparatus having the above first feature and being characterized in that the developing unit has a support shaft supported by the housing and is caused to rotate by the repulsive force of the elastic members so that the developer roller comes into pressing contact with the photoconductor.
A third feature of the present invention resides in the image forming apparatus having the above first feature and being characterized in that the toner cartridge is formed with projections at positions against which the elastic members are abutted.
A fourth feature of the present invention resides in the image forming apparatus having the above second feature and being characterized in that the toner cartridge is formed with projections at positions against which the elastic members are abutted.
According to the first feature of the present invention, the elastic members fixed at one end thereof to the housing are provided, and when the toner cartridge is set into the framework of the developing unit, the distal ends of the elastic members abut the toner cartridge so that the elastic members are compressed to produce repulsive force, which acts on the developer roller by way of the toner cartridge and framework so that the developer roller comes into pressing contact with the photoconductor.
According to the second feature of the present invention, since the developing unit has a support shaft that is supported by the housing, the developing unit is caused to rotate by the repulsive force of the elastic members so that the developer roller comes into pressing contact with the photoconductor.
According to the third and fourth features of the present invention, since projections are formed at positions against which the elastic members are abutted, the repulsive force is received by projections alone when the toner cartridge is attached to the developing unit.